I've been trying to find information on choosing an NPN transistor but everything I've found seems to apply to saturated transistors only. I'm basically trying to amplify the current given from a 3mm audio headphone jack to a useful level. Knowing the voltage and current required for the load at the collector, plus the voltage and current supplied to the base how can I determine from a spec sheet if a transistor is suitable?
Also, am I correct in thinking that the voltage supplied by the audio source will need to be at least 0.6V?
EDIT: For the sake of an example let's say the load is a bunch of LED's totaling 9V and 800mA. Obviously with an appropriate power source. I'm still researching the current and voltage of the audio signal but for this example let's say it's 0.3V and 5mA.